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leading-edge-vortex
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Canard-wing interactions in subsonic flow
, Article Iranian Journal of Science and Technology - Transactions of Mechanical Engineering ; Volume 37, Issue M2 , 2013 , Pages 133-147 ; 22286187 (ISSN) ; Davari, A. R ; Soltani, M. R ; Sharif University of Technology
Shiraz University
2013
Abstract
Extensive subsonic wind tunnel tests were conducted on a coplanar wing-canard configuration at various angles of attack. In these experiments, a 60° swept canard was placed upstream of a 60° swept main delta wing. This paper deals with the distribution of mean and fluctuating pressure coefficients on the upper surfaces of both the canard and the wing immersed in a variety of angles of attack. According to the results, presence of canard postpones the vortex formation and growth on the wing to higher angles of attack compared to the canard-off case. Due to the canard downwash field, the wing operates at lower effective angles of attack and therefore, its vortex breakdown is delayed. The...
Experimental Investigation of Leading Edge Flow Control for a Rigid Flapping Wing Using Plasma Actuator
, M.Sc. Thesis Sharif University of Technology ; Ebrahimi, Abbas (Supervisor)
Abstract
Using flapping motions, birds produce aerodynamic forces required to fly. Flapping wing aerodynamics is one of the most complicated problems in unsteady aerodynamic field. Experimental study on the structure, the way of production and growth and the feasibility of controlling the leading edge vortex are the main goals of this research in order to improve the aerodynamic performance of flapping wings. Since leading edge vortex structure appears in both upstroke and downstroke of a complete storke in flapping motion, controlling the structure in one of the half-storkes can provide the possibility of having a better aerodynamic performance. In this research, the wing is designed and...
Investigation of the Leading Edge Flap Effects on the Aerodynamic Coefficients of a Cranked Arrow Delta Wing
, M.Sc. Thesis Sharif University of Technology ; Soltani, Mohammad Reza (Supervisor)
Abstract
In this study, investigated the simulation flow over a double-delta wing. The flow field was simulated by three dimension grid and RANS flow equation by K-ω-SST model. In order to investigate effect of AOA and leading edge flap simulated variable AOA and leading edge flap angle. The results shows created two vortex in inside and outside the wing. The vortex burst at high AOA and the Lift decrease after vortex bursting. The using leading edge flap effect on the vortex power and postpone vortex bursting and increasing wing lift coefficient in the high AOA. Also the leading edge flap effect on the pitch moment coefficient and change the pitch moment coefficient curve slope. The other effects of...
Aerodynamic Control of Flow Around a Rigid Wing in Flapping Motion Using Geometry Modification Methods
, M.Sc. Thesis Sharif University of Technology ; Ebrahimi, Abbas (Supervisor) ; Farahani, Mohammad (Supervisor)
Abstract
The physics of the flow around the wing in the oscillatory motion of the wing has various patterns, including the leading edge vortex, the tip vortex and trailing edge vortex escape. The interaction of these vortices forms a complex flow structure around the wing, which will have a direct effect on the aerodynamic performance of the wing. Therefore, controlling these structures can be considered as a way to improve the performance of the flapping wing. One of the passive flow control techniques that has recently been taken into consideration is a leading-edge protuberance method. Another type of passive flow control is geometric correction, using corrugation method. According to studies, two...
Energy Extraction from Two Oscillating Airfoils in Tandem Configuration at Low-Reynolds-number Turbulent Flow
, M.Sc. Thesis Sharif University of Technology ; Ebrahimi, Abbas (Supervisor)
Abstract
In this study, the physic of an unsteady flow surrounding two oscillating airfoils in tandem configuration at low Reynolds-numbers has been simulated in a 2D manner by utilizing the Sliding-mesh approach and K-ω-SST turbulent model in Ansys-Fluent application. The first step in this study is selecting the decent numerical grid and flow solution scheme. After choosing the proper solution for this problem, next is to verify the methodology with respect to the references. In the next step, The tandem configuration and pitching motion of the airfoils is being implemented with existing tools and the flow structure, leading-edge and trailing-edge vortex shedding and blade-vortex interactions is...
Canard flow improvement in a split canard configuration
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 229, Issue 6 , 2015 , Pages 1076-1087 ; 09544100 (ISSN) ; Askari, F ; Soltani, M. R ; Sharif University of Technology
Abstract
Extensive low-speed wind-tunnel tests are performed to study the flow field structure over a dual-surface canard, known as split canard, in comparison to the conventional configurations. Surface pressure for both steady deflections and unsteady oscillations of the canard are measured and compared for both canard-alone and split-canard cases. The split canard shows a superior advantage at high angles of attack, where a delay in the vortex breakdown phenomena on the canard surface is observed. For the split-canard configuration, the downwash of the front canard reduces the effective angle of attack at the inboard section of the rear element which postpones formation of the leading-edge vortex....
Effects of canard position on wing surface pressure
, Article Scientia Iranica ; Volume 17, Issue 2 B , 2010 , Pages 136-145 ; 10263098 (ISSN) ; Askari, F ; Davari, A. R ; Nayebzadeh, A ; Sharif University of Technology
2010
Abstract
A series of wind tunnel tests were performed to study the effects of a canard and its position on the downstream flowfield over the wing surface. The wing surface pressure was measured for both canard-off and canard-on configurations. In addition, the canard position effects on the wing were investigated at different angles of attack. The canard was installed at three vertical positions and at two different horizontal distances from the wing apex. The results show a remarkable increase in the wing suction peak for the canard-on configurations. At low to moderate angles of attack, among the various configurations examined in the present experiments, the mid-canard configuration developed a...
Experimental investigation of the leading edge vortex formation on unsteady boundary layer
, Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 232, Issue 18 , 2018 , Pages 3263-3280 ; 09544062 (ISSN) ; Abdollahi, R ; Azimizadeh, E ; Sharif University of Technology
Abstract
Extensive experimental studies have been performed to investigate the unsteady boundary layer behavior over a plunging wind turbine blade section. The studies have been undertaken at various combinations of reduced frequencies, Reynolds numbers, and locations. A boundary layer rake has been carefully manufactured and utilized for velocity measurements inside the unsteady boundary layer. The measurement has been conducted in pre-static stall conditions. The reduced frequency and free stream velocity have varied from 0.005 to 0.1, and 30 to 60 m/s, respectively. To cover all possible scenarios, the streamwise positions of measurements have been chosen to be in favorable (x/c = 0.37), almost...
Impact of dielectric barrier discharge plasma on the wake of a wind turbine blade section oscillating in plunge
, Article Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy ; Volume 236, Issue 2 , 2022 , Pages 320-335 ; 09576509 (ISSN) ; Davari, A. R ; Soltani, M. R ; Sharif University of Technology
SAGE Publications Ltd
2022
Abstract
Effects of dielectric barrier discharge plasma have been studied on the wake velocity profiles of a section of a 660 kW wind turbine blade in plunging motion in a wind tunnel. The corresponding unsteady velocity profiles show remarkable improvement when the plasma actuators were operating and the angles of attack of the model were beyond the static stall angles of the airfoil. As a result the drag force was considerably reduced. It is further observed that the plasma-induced flow attenuates the leading edge vortices that are periodically shed into wake and diminishes the large eddies downstream. The favorable effects of the plasma augmentation are shown to occur near the uppermost and...